A supporting device supports an in-vehicle mounted object on a vehicle body. The supporting device includes a bracket and an elastic member. The bracket has a side-plate part having an opening part. The elastic member is engaged with the first opening part so as to be provided between the bracket and the in-vehicle mounted object. The side-plate part includes a notch having one end connected to the opening part and the other end open outward. The notch does not intersect with a plane containing a line passing substantially a center of the opening part and extending in a main vibrating direction of the in-vehicle mounted object, the plane being substantially perpendicular to the side-plate part.